A group of spies called the 5446 Corps were trained by North Korean elite special forces since their youth, ostensibly towards the lofty goal of unifying Korea. They are ambitiously dispatched to South Korea, where each disguises himself as a fool, an aspiring singer, and a high school student. Passing boring time without receiving any orders from the North, they gradually get used to life as ordinary neighbors in a small town until one day, their mundane lives are turned upside down when a "secret and great" mission is suddenly assigned to them. Due to the events of the Second Battle of Yeonpyeong, South Korea demands the names, location, and rank of 30 North Korean spies active in South Korea, promising financial aid to the North on the condition that Pyongyang turns in their spies. To prevent the elites from falling into enemy hands, the North Korean government orders dozens of active duty spies to take their own lives. Meanwhile, their North Korean army instructor Kim Tae-won crosses the border to eliminate those who refuse to follow.
The story is about two Korean National Police University students, Ki-joon (Park Seo-joon) and Hee-yeol (Kang Ha-neul), who witness a kidnapping and track it down. However, the authorities are busy with the kidnapping of a son of a business mogul. They decide to embark on their own amateur investigation, which gets them into all sorts of trouble.
A rock climber tries to save the day when a mysterious white gas envelopes an entire district in Seoul, South Korea.
One fateful day, on his eighteenth birthday, Woo-jin wakes up to see a face and body that is not his own. He is very shocked and confused, he confronts his mother with his new appearance and she is also shocked but tearfully accepts him for who he is. With the help of his mother (Mun Suk) and his best friend (Song-beck), Woo-jin is able to cope with his strange condition. Ever since this day Woo-jin, now a furniture designer, wakes up in a different body every day, regardless of age, gender and nationality. Sometimes he's a man, a woman, old, young, or even a foreigner. He can even speak different languages, depending on who he is for the day. He's the same person on the inside, but on the outside he's always someone new. Looking at a different face in the mirror every morning is hard for him to get used to.
Kim Jae-hyun (Yoo Yeon-seok) is a sports manager and former talented basketball player. His only wish is to send a novice and promising player Kang Chul to America. To fulfill his wish, he must head to Busan to find and convince Kang Chul. Meanwhile, Bae Soo-jung (Moon Chae-won) works in an advertising agency and must also travel to Busan for a business trip. The two meet on the Korea Train Express and spend 24 hours in the unfamiliar city of Busan, South Korea.
Instead of calling her boyfriend, Yoon-jung accidentally calls a total stranger, Hyun-seung, a man who is having trouble getting over his ex-girlfriend. She ends up having phone sex with him and later, they become comfortable with each other and start talking about their respective relationship problems. They eventually decide to meet and a more intimate friendship develops, which leads to both falling for each other.
A honest cop seeks justice for a common man against all odds. A rich boy seeks revenge on the cop.
Jong-Woo (Shin Ha-kyun) went to prison four times for petty crimes likes burglary and car theft, but he now works as an auto mechanic. He has a 17-year-old son named Gi-Hyuk (Lee Min-ho (actor born 1993)), which he raises by himself. Gi-Hyuk is a smart kid, but troubled. The father and the son also do not get along. Although, Jong-Woo might appear like an irresponsible father, he tries his best and even works at night as a private taxi service.